crappy audio; can you help?

Randy Brown wrote on 4/19/2006, 11:23 AM

Hi,
I posted this on the vegas audio forum but had no replies; I thought I'd see if I would have any luck here:
This past weekend we shot a benefit concert (Michael Martin Murphey with an orchestra). I ran a stereo pair (XLR connections) into one camera to pick up ambience; doesn't sound awful but they were placed in the back (and sounds like it). I also got a stereo line feed from the board (XLR balanced). There was hardly time to set up and later found out that I was only receiving one channel (not a big deal though since he was running mono anyway).
Anyway, to be safe, I adjusted the signal to peak at about -20 db. It seems the signal was too hot from him (sound man) as the wave form doesn't look clipped ( no squared off tops) but it sounds clipped at times. I took it into Sound Forge and (of course) "clipped peak restorage" didn't help but the "click and crack removal" helped somewhat but still doesn't sound good. I'm wondering if one of you guys might be able to sweeten it up a bit.
The plan is to have it aired on CMT, a local CBS affiliate (KFDA Amarillo,TX) and PBS. If the audio can't be fixed I may have to scrap it.
If you can help I could give you a special thanks in the credits and send you a copy on DVD.
If you'd like to give it a shot please email randy( at )crystalclearnm.com and I'll send a short .wav and we can go from there.
TIA,
Randy

Comments

farss wrote on 4/19/2006, 4:02 PM

To get Clipped Peak Restoration to work the clipped peaks have to be hard digital clips. In other words if they were clipped prior to going into the digital converters in the camera then they'll likely not be at 0dBFS and if they were clipped in the analogue domain (in which case it's actually distorted rather than clipped) then again the tool will not work.
My trick is to open in SF, adjust the volume using the Volume FX to create hard digital clipping and then use the Restore Clipped Peaks tool. Also you can get a situation where +Ve peaks are more / less clipped than -Ve peaks, again you need to get both of them hard clipped.

This can work remarkably well or be completely useless. For simple waveforms it works very well. With bad clipping of complex sounds it's useless. Way too much data has been lost. The tool will restore the peaks but what's happened is other data got lost during clipping so it cannot be restored.

Bob.

Randy Brown wrote on 4/20/2006, 8:26 AM

Thanks Bob,
The problem is only noticeable in a couple of spots and if you mix the 2 tracks together (mics and line feed) it's not absolutely terrible but probably not good enough for national TV; however even if the data is lost I'd like to try to make it a little fatter and eq out the occasional hot and ringing bass guitar notes; SF and Vegas seem to only have a 20 band eq, do you know where I can find say a (software) 32 band eq (or do I just not see it in SF)?
Thanks again Bob,
Randy

farss wrote on 4/20/2006, 1:38 PM

There's a parametric Eq in SF which if one can believe the graphs should give you very narrow notch filters, you can also try stacking filters to get more rejection.
You can also use NR2 as a filter, just sample part of the note. I've used it to remove a note from behind a word with some success.
Bob.

craftech wrote on 4/20/2006, 2:22 PM

Randy,
Try some of these free plugins from Pacific Soundcraft. They show up in Vegas with the other third party plugins after you install them and seem to work better than the Vegas equivalent plugins. The limiter is a read ahead optimizer that seems to work very well even at the default settings to reduce clipping. The noise gate works just as well.

John